This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. MRI Assessment of Pallidotomy Lesion Placement and Post-operative Localization in Parkinson's Disease In recent years, the use of radiofrequency ventroposterior pallidotomy (VPP) as a symptomatic treatment for the medically refractory motor symptoms of Parkinson[unreadable]s disease (PD) has been gaining widespread acceptance. A number of centers have reported significant improvements in controlling disabling dyskinesias, on/off fluctuations and other motor symptoms in patients with idiopathic PD (Baron et al., 1996;Dogali et al., 1995;Iacono et al., 1995;Johansson et al., 1997;Lang et al., 1997;Laitinen et al., 1992a;Laitinen et al., 1992b;Lozano et al., 1995;Uitti et al., 1997). Although there is a general agreement that VPP is helpful for many patients, results vary considerably between patients and centers performing the operation. One reason for this variability is likely due to differences in lesion placement and size.